It would be an epic confrontation between evenly matched opponants. the fight would go on for human generations with each learning as the fight goes on. We already know Preds can live more than 200 years, so the battle would last for over a hundred years until the Terminator's existing power cell depleted in 150 years (but it would probably be less time with all the extra energy used to combat such a foe as a Pred). However, if the Terminator found another power source or upgraded, that would change the whole scope of things.
One important thought though: Unless the Terminator was set to kill the Pred to begin with, or the Pred were protecting the Term's target, why would the Terminator bother fighting. It doesn't care about self preservation outside of remaining functional until its mission is accomplished.
I guess the real question first is what's their motivation for fighting, and how the hell does a Pred fit into the battle against Skynet?
If somehow we do get to see this movie, my money is on the P-800 Predinator Endoskeleton which won't be nearly the b1tch the Predalien was. Imagine a T-600 with a endo Pred head on it. Let's see Hot Toys make that.
Screw it, I'll make that when I get a T-600.